This invention relates to a tension providing device which enhances the stability of a spring.
Especially, this invention relates to a locking mechanism in a tension providing device which is simple in construction and is unnecessary for maintenance together with providing the maximum stability in the spring, thereby being allowed to lock or release the stability.
In general, "tension providing device" means a device always allowed to provide a pushing force in a fixed direction and possible to display a resistance force approximately the same as that of a rigid body when said device is subjected to a reaction force the counter-direction against said pushing force.
The above mentioned tension providing device, for instance, is used at a position where characteristics of the rigid body are requested when a reaction force in the counter-direction acts on a chain or a belt tensioner which is always pressed by a pushing force in a fixed direction. In other words, the chain tensioner gives a certain tension to a chain or a belt pressing it in the fixed direction when slackness occurs in said chain or said belt because of elongation or the wear and tear during the use. In this case, it is desirable that said device has characteristics nearly the same as that of the rigid body.
However, among said desirable tensioners, there exist such ones which are controlled by handling according to the elongation of the chain or the like or automatically. The former is a mechanical device and is comparatively cheap, but has such defects as difficulty in maintenance, generation of an abnormal sound because of being a perfect rigid body in the direction of the reaction force thereof and thereby increasing the wear and tear of the tension undurable to the use for a long period.
Further, the latter is a device which avails an oil pressure apparatus or the like and has such defects as the complication of a whole apparatus, the difficulty in treatment and a high price.
Heretofore, the tension providing device is provided with a mechanism having no necessity of maintenance as shown in FIG. 1. However, in this locking mechanism, the outer circumference of a piston 1 is pressed with a cap screw 7 and therefore the locking of the pushing force (in a direction shown with an arrow) is not sure and said cap screw 7 is apt to fall off. Furthermore, when this device is incorporated in an engine or other apparatuses, an oil leakage occurs from said cap screw portion or a wear and tear caused by a hair crack on a sliding surface which occurs by pressing the sliding portion of the piston 1 with said cap screw 7 directly. Still further, since the incorporation of the cap screw 7 in the device makes the control of the tensioner impossible, the exposure part of the device increases, thereby being impossible to make compact.
Further, since it is impossible to confirm the condition such as locking or unlocking of the pushing force in said device from outside, said device has such defects as taking much times in assembling, incorporating in an apparatus or control during the periodical inspection and is not used practically. Furthermore, in FIG. 1 the numeral 2 is a cylinder, 3 is a shoe integrated with the piston 1, 4 is a male screw, 5 is a spiral spring and the numeral 6 is a fixed pin.